> Chris Ball wrote:>> Hi,>>>> > Mmm.. btrfs appears to configure itself as a "pseudo" filesystem,>> > which is why it returns fake device numbers via stat(), similar>> > to procfs or sysfs.>>>> Probably because a single btrfs filesystem can be composed of multiple>> devices; one major/minor would not be sufficient.> ..> > So I'm seeing in the code.> > But for the 99% common case (personal computers, one drive), it would be> rather useful it it would comply with filesystem standards there.> > In the unlikely event that a btrfs actually is composed of multiple > devices,> then in that case perhaps return something nonsensical.> > Mmm.. don't we already *have* an LVM layer in Linux?> > Seems like a rather bad idea to have a new Linux-specific> filesystem re-implement it's own private LVM, and thus> confuse various disk management tools and the like...

[added linux-kernel to CC: list]

Along those lines -- since btrfs reports invalid device information to stat(2),then I would suggest that it should also return -ENOTSUP for the FIBMAP and FIEMAPioctl() calls. Otherwise, somebody's filesystem is going to get corrupted.